Dosage control apparatus

ABSTRACT

The invention is directed to a dose control apparatus. The apparatus has two armatures pressed against a valve seat by at least one spring. A coil induces a magnetic field that motivates the armatures against the force of the spring, thereby opening the valve. The armatures may move along a common axis in opposite directions. The apparatus may also include a core located between the armatures and a casing about the coil. The core and casing act to guide the magnetic field, reducing the power requirements for creating the field. Current may be periodically reversed in the coil to provide a degaussing field. In addition, a signal may be produced by the coil in the presence an externally applied magnetic field such as an MRI. An opposing magnetic field may be produced by the coil or the current provided to the coil may be adjusted.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/065,726, filed Feb. 25, 2005, now U.S. Pat. No. 7,588,046, which wasa continuation of U.S. application Ser. No. 10/331,425, filed Dec. 30,2002, now U.S. Pat. No. 6,880,564, which claims the benefit of U.S.Provisional Application No. 60/412,365, filed Sep. 20, 2002, which isincorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

This invention, in general, relates to an implantable drug deliverysystem. More specifically, this invention relates to a dose controlsystem and valves used to manipulate the delivery rate of apharmaceutical solution.

BACKGROUND OF THE INVENTION

Implantable drug infusion therapy has been used to treat variousailments including pain management and diabetes. These drug pumps anddelivery systems have been used to deliver pain medication, hormonessuch as insulin, and other pharmaceutical agents. For example,intraspinal drug delivery may be used to treat chronic pain. Byutilizing these systems, pharmaceutical agents are delivered inrelatively lower doses to a specific region of treatment. In thismanner, full body dilution and membrane barriers are avoided. Similarly,insulin may be delivered without the inconvenience of injections.

Infusion pumps come in several varieties. Some infusion pumps areconstant rate such as those driven by gas pressures or springs. Othersare variable rate pumps driven by hydration of an expandable substanceor a variable rate pumping mechanism.

Implantable drug delivery systems have several advantages over externaldrug pumps, oral medications, suppositories, and injections. Theseimplantable systems are unobtrusive, unencumbering, and typicallydeliver smaller doses to targeted regions. Pills, suppositories, andinjections deliver large doses of pharmaceutical agents that passthrough a large portion of the body to reach the treatment area. Thelarge dilution ratio caused by this passing requires a large dose toachieve an effective concentration in the treatment area. In addition,patients must remember to administer the correct dose at the appropriatetime to achieve the desired therapeutic levels of the pharmaceuticalagent in the treatment area.

While external infusion pumps overcome some of the limitations of pills,injections, and suppositories, they are often cumbersome andinconvenient. These devices must typically be worn or strapped to thepatient, encumbering clothing selection and presenting a risk of damageto the external pump. In addition, catheter incision points are subjectto infection.

However, current versions of implantable infusion pump systems also havedisadvantages. Typically, implantable infusion pump systems providelimited programmability and patient control. In addition, access to thepump system is limited. Some pump systems have a constant rate whileothers attempt to control flow rates by varying pump speeds or hydrationrates. In the case of constant rate pumps, prescription rates are set bythe selected flow restrictor and pump pressure. In the case of variablerate pumps, prescriptions are limited by the available rate settingsassociated with the pump.

Patients generally have no control over the prescription. In painmanagement cases, this can lead to periods of under dosing and periodsof unnecessary over treatment. Doctors are also limited in the selectionof prescriptions and often must have an office visit with patients toadjust prescriptions. These adjustments are expensive to insurancecompanies, unprofitable for doctors, and inconvenient for patients.

In the case of other treatments such as insulin treatment, the requiredprescription varies with the behavior and environment of the patient.Insulin requirements increase with carbohydrate laden meals and decreasewith activity. Excess insulin can lead to shock and low insulin can leadto excess blood sugar levels and many long-term health problems.

Another problem with implantable infusion pumps is determining actualdosage rates and predicting reservoir levels. Limited access to the pumpmeans expensive preemptory refilling. Typical implantable infusion pumpsdo not maintain rate data useful in determining actual dosage schedulesand reservoir levels. Therefore, doctors have difficulty predictingreservoir levels. This often leads to wasted pharmaceutical solution.Worse, the reservoir may empty and patents may suffer from a lack oftreatment.

A further problem with current dose control systems lies in their methodfor controlling dose rates. These methods often use many mechanicalparts that may wear. Further, these systems use parts that maymalfunction under externally applied magnetic fields such as those of anMRI.

As such, typical infusion pumps suffer from deficiencies in providingprescription options, actual prescription rate data, and control ofdosage. Many other problems and disadvantages of the prior art willbecome apparent to one skilled in the art after comparing such prior artwith the present invention as described herein.

SUMMARY OF THE INVENTION

Aspects of the invention may be found in an apparatus for controllingthe flow of a treatment solution. The apparatus includes a housingsurrounding an enclosure and having two ports in communication with theenclosure. Each port has a valve seat surrounding the port opening.Further, each port has an associated armature with head pressed againstthe valve seat by a spring. At least one coil is used to create amagnetic field, which generates a force opposing the spring force,thereby opening the valve. In one case, the spring is the same springpressing both armature heads against the valve seats. The armatures mayhave a common central axis and move along this axis in oppositedirections. A core or spring stop assembly may be placed between thearmatures. A covering of magnetically permeable material may be placedabout the coil. The core and covering may be used to direct the magneticfield.

The coil may also be used to measure a signal response indicative of anexternal magnetic field. A flow control module may implement in the coila signal that induces a magnetic field to oppose the external magneticfield or a degaussing field.

Additional aspects of the invention are found in a method forcontrolling the flow rate of a treatment solution. A valve is providedwith two armatures pressed against valve seats by at least one spring. Acoil is activated to induce a magnetic field that motivates thearmatures to move against the force of the spring and open the valve.The method may further include interpreting a signal from the coil toascertain the presence or strength of an externally applied magneticfield. A signal may be sent to the coil to induce an opposing field or adegaussing field.

As such, a dose control apparatus is described. Other aspects,advantages and novel features of the present invention will becomeapparent from the detailed description of the invention when consideredin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention andadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings in which likereference numbers indicate like features and wherein:

FIGS. 1A and 1B are schematic diagrams of the system, according to oneembodiment of the present invention;

FIG. 2 is a schematic block diagram depicting a dose control module foruse by the system as seen in FIG. 1A;

FIGS. 3 and 4 are schematic block diagrams depicting exemplaryembodiments of a dose control module as seen in FIG. 2;

FIGS. 5, 6, 7, and 8 are block flow diagrams depicting exemplary methodsfor use by the dose control module of FIG. 2;

FIGS. 9A, 9B, 9C and 9D are schematic diagrams depicting an exemplaryembodiment of a valve for use in the system as seen in FIG. 1A;

FIGS. 10A, 10B, 10C and 10D are schematic block diagrams showing anotherexemplary embodiment of a valve for use in the system as seen in FIG.1A;

FIG. 11 is a schematic diagram depicting a further exemplary embodimentof a valve for use by the system as seen in FIG. 1A;

FIG. 12 is a block flow diagram depicting an exemplary method for use bythe system as seen in FIG. 1A;

FIGS. 13, 14, and 15 are schematic diagrams depicting an exemplaryembodiment of a valve for use by the system as seen in FIG. 1A;

FIG. 16 is a graph depicting an inductance field resulting from a pulsesignal for use by the valve as seen in FIGS. 13, 14, and 15;

FIG. 17 is a schematic diagram of a circuit for producing the inductancefield of FIG. 16;

FIG. 18 is a block flow diagram depicting an exemplary method for use bythe system as seen in FIGS. 13, 14, and 15;

FIG. 19 is a schematic diagram of a circuit for use by the system asseen in FIG. 1A; and

FIG. 20 is a block flow diagram of an exemplary method for use by thesystem as seen in FIG. 1A.

DETAILED DESCRIPTION OF THE INVENTION

Implantable drug treatment therapy is useful in treating a variety ofailments such as chronic pain management, insulin-dependent diabetes,chemotherapy (systematic and targeted), Myelin treatment, andneurotransmitter treatment, among others. In each of these examples,patients could benefit from greater variety of prescriptions, morecontrol, and accurate monitoring of reservoir levels.

For example, in the case of pain management, patients may benefit fromselectively applying various doses based on need. A preset array ofprescription levels would permit the patient to adjust treatment basedon pain, increasing as needed and decreasing otherwise. Limits and otherconditions may be established to prevent over dosing. Such a systemwould permit a patient to compensate for developing tolerances oradvancing pain.

Patients can also benefit from having more than one pharmaceutical agentor treatment solution delivered to the treatment area. Differing rate ofdrug delivery for different drugs can be effective for pain management.For example, one pharmaceutical agent may be infused for low-level painwhile another is introduced only during extreme pain. In this manner,tolerance development may be moderated for the stronger drugs, or ratesmay be varied for those that are more expensive.

Similarly, treatments such as insulin treatments may be managed moreeffectively with more patient control and multiple treatment solutions.For example, a patient may modify dose with activity and consumption.Further, agents with varying time-release patterns, co-factors, andsupplements may be introduced with varying rates.

Such a delivery pattern is realized with a separate dose control system.FIG. 1A depicts an embodiment 1 of the present invention. A pressurizeddrug cavity 2 delivers a treatment solution through a filter 3 and flowrestriction 4 to valves 5 and 6. However, various motivating systems maybe envisaged for supplying valves 5 and 6 with treatment solutions. Thecircuitry 7 using energy from battery 8 manipulates the valves 5 and 6to produce a flow rate in accordance with a prescription. However, one,two, or more valves may be used. The treatment solution may then travelthrough a catheter 11 to a treatment region in a patient. A bolus cavity9 may be located inline to provide for the administering of bolusdosages.

The circuitry 7 and battery 8 comprise a dose control module and may belocated separate from other elements as denoted by the enclosure 13.However, other elements such as the valves 5 and 6 may be included withthe circuitry 7 and battery 8 as indicated by the enclosure 15. Thebolus cavity 9 may also be enclosed with the circuitry 7 and battery 8.The drug cavity 2, filter 3, and flow restriction 4 may be located in aseparate housing.

Moreover, various valve configurations may be envisioned. Valves 5 and 6may be placed in series, parallel, or other arrangements. One, two, ormore valves may be included in addition to restrictions to formulatevarious configurations.

FIG. 1B shows another embodiment 10 of the present invention. FIG. 1Bhas an infusion pump 14 implanted in a patient 12. From the infusionpump, a catheter 20 leads through a dose control module 18 to atreatment area 22. The dose control module 18 may have a valve set 16 orother means of directing dosage. Alternately, the dose control module 18may have a communication link 26 with the infusion pump 14 or valve setthat aids in controlling dose. The system may also include an externalpatient control unit 24. The external patient control unit may directthe dose control module 18 to change dose rates or prescriptionconfigurations. In addition, other infusion pumps 28 may be connectedwith the dose control module 18 or valve set 16 such that multiplepharmaceutical solutions are delivered through the catheter 20 to thetreatment area 22.

The system may be useful in treating various ailments. For example, thetreatment area 22 may be intraspinal. The infusion pump 14 may deliver amorphate or other pain modifying pharmaceutical solutions through thedose control module 18, valve configuration 16, and catheter 20. Inanother case, the infusion pump 14 may deliver insulin through a dosecontrol module 18 and catheter 20 to be absorbed by the bloodstream.

The patient control unit 24 may be used to modify dosage to eithercontrol pain in the case of a pain medication or control blood sugar inthe case of insulin delivery. For example, the patient control unit 24may permit the patient to select a prescription from a preset array ofprescriptions which is then transmitted the dose control module 18.

A separate dose control module 18, as shown, provides aninterchangeable, flexible, dose control solution for implantable druginfusion therapy. Doctors may select a dose control module based on theprescription range, while using a pump with a constant flow rate.Surgeons may also implant multiple infusion pumps and connect them to asingle dose control module. In addition, doctors may establish a set ofprescriptions selectable by a patient and observe actual dosage rates.

To manipulate dosage rate, the dose control module 18 sends timedependent signals to dose or flow manipulating devices such as valvesand pumps, among others. A desired dosage rate may be achieved byopening a valve for a specific period of time. Alternately, the signalmay open and close the valve such that a time averaged dose rate isachieved.

FIG. 2 depicts an exemplary dose control module 30. Within ahermetically sealed housing, the dose control module 30 may have aprocessor 32, instructions 34, prescription settings 36, a flow meter38, a clock 40, a control circuitry 42, a communications interface 44, adata storage 46, security instructions 48, a power supply 50, dosemanipulators 52, and dose manipulator state sensors 54, among others.However, these elements may or may not be included. Further, they may behoused together, separate or in various combinations, among others.

Processor 32 functions to interpret instructions 34 in view ofprescription settings 36 and other data 46. The processor 32 interactswith control circuitry 42 to establish dosage rates and dose pathsthrough the valves and restrictors 52. The instructions 34 are softwareinstructions for implementing the various methods used by the dosecontrol module 30 and may include instructions for establishing valveconfigurations, determining the dose rate, calculating effectivestrength, determining dosage, comparing dosage to predetermined limits,determining valve position, and communicating with other devices, amongothers.

The prescription settings 36 take the form of parameters associated witha prescription. These parameters may include dose rates, degradationrates, model parameters, limits, and conditions, among others. Forexample, a prescription setting 36 may be a dose rate of 0.8 millilitersper day, with further limits of three hours at that rate for a limit of0.3 milliliters over any given 12 hours. In another example, theprescription rate may be expressed in .mu.g/day with a degradation modelto determine a corresponding dose rate. However, various dose rates,limits, and conditions may be associated with various therapies.

The dose control module 30 may include a flow meter 38. The flow meter38 may take various forms including a pressure drop sensor, a rotarymeter, a switch, and a force meter, among others. Alternately, the flowmeter may calculate flow rates from known pump rates and valvepositions.

The system may also include a clock 40. The clock 40 may be used increating timed signals for manipulating dosage rates. The clock 40 mayalso be used for determining whether dosage has exceeded thepredetermined limitations. Further, the clock 40 may be used to recordtime stamped data. The clock 40 may be used to determine time of day,time differences, and total time implanted, among others. With the clock40 and the flow meter 38, actual dosage data may be recorded, limits andconditions tested, and reservoir levels calculated. The benefits includean understanding of dosage rates, better prediction of reservoir levels,and more accurate adherence to overdose safety limits. Additionalcounters may be used to count fills and other parameters.

The control circuitry 42 is used to establish valve position or doserates. This is accomplished by selectively sending signals to dosemanipulators such as valves and pumps. The processor in accordance withthe instructions 34 and the prescription settings 36 directs the controlcircuitry to create signals, manipulating valve position to control doserates.

The communications interface 44 may take various forms including aninterface with an external computer prior to implanting, or aradiofrequency interface to external devices. With a connection to acomputer, the dose control module 30 may be programmed and configuredprior to implanting. Once implanted, a doctor may interface with thedevice to establish prescription settings 36, download or upload otherdata from the data storage 46, and determine reservoir levels, amongother data. With a patient control unit, a patient may choose aprescription selected from a set of prescriptions preset by thepatient's doctor.

The dose control module 30 includes a data storage 46. The data storage46 may store time-stamped dose data, dosage data, other parametersassociated with valves, restrictors and device configuration, calculatedreservoir levels, and other data. The data storage may take the form ofvarious RAM or flash memories, among others. The data may also betransmitted and stored on a patient control unit.

The dose control module 30 may also include security instructions 48.These security instructions can include encryption algorithms orauthentication methods such as device identification numbers to limitaccess to the functionality of the dose control module 30.Communications with unauthorized devices may be ignored or limited intheir access to alter prescriptions.

The power supply 50 may take the form of a battery. The power supply mayalso include a means of recharging from an externally applied RF signal.The system may also monitor the power supply 50. If the power supply 50reaches a low level or power is lost, the system may include fail-safeelectronic circuitry that could place the valves in a safe position orthe valve design can default to a safe configuration prior to the lossof power. For example, a reserve power supply or capacitor may directthe closing of all valves.

The dose control module may also include dose manipulators such asvalves and restrictions. These dose manipulators may be arranged invarious configurations to provide a variety of dosage rates andprescription configurations. Using various valve configurations, thedose control module may also deliver more than one drug, implement bolusinfusions, and permit a variety of pharmaceutical delivery rates to oneor more catheters. However, the valves may also be located external tothe dose control module 30.

The dose control module 30 may also include position sensors 54 fordetermining the position of valves or state of dose manipulators 52.Alternately, the dose control module may use signals produced by thecontrol circuitry 42 and processed by the processor 32 to determine thevalve position. For example, signal response from an inductance coil maybe used to determine the position of a valve core.

FIG. 3 depicts another embodiment of a dose control module 76. The dosecontrol module 70 includes a microprocessor 72. The dose control module70 may be programmed using a programming module 74. Instructions for themicroprocessor may be stored in the programming memory 76 andprescription parameters may be stored in the memory 78. Alternately,instructions may be received through the receiver/transmitter 82.

The program memory 76 may take the form of ROM, RAM, or flash memory,among others. Similarly, the memory 78 may take the form of ROM, RAM orflash memory, among others.

The system may also include a clock 80 for time stamping data,determining whether dosage limit conditions have been met, and producingtime sensitive signals, among others. For example, the clock may be usedin creating an electromagnetic pulse signal for maintaining a minimummagnetic field about an inductance coil. The clock can also be used indetermining a dosage ratio or total dosage for comparison with limitsand conditions.

The power supply module 84 may provide power to the microprocessor.Further, it may be used on conjunction with a voltage multiplier 86 tocontrol valve position. In accordance with the prescription parametersand the instructions stored in the program memory, the microprocessor 72may provide electromagnetic signals to valves, directing the opening andclosing of those valves using a pulse amplitude and width controller 88and switch matrix 90.

The dose control module may be housed in a module, separate from a pumpand reservoir. Valves, restrictions, and other dose manipulators may beincluded in the module or housed separately. In this manner, a singledose control module may manipulate dose rates associated with more thanone pharmaceutical solution and/or multiple valves to achieve a selectedprescription.

The patient control unit may have a circuitry similar to that shown inFIG. 3. The patient control unit may have a processor, various memories,a clock, a receiver/transmitter, a power supply, and a programmingmodulator interface. With these elements the patient control unit maycommunicate prescription selection and other data with the dose controlmodule.

FIG. 4 depicts an exemplary valve array 110. The electronics 112 and thedose control module communicate through one or more control lines 114 toa set of valves 118, 120, 122 and 124. The system may also includevarious restrictors 116 and 126.

In this exemplary embodiment, a therapeutic solution enters the inletand may pass through a restriction 116 if one is in place. The valvesare configured to deliver the desired dose rate through the outletcatheter 128. The valves may be configured in parallel using valves 118and 122. Alternately, the valves may be configured in series usingvalves 118 and 120. Further, the valves may be configured in variouscomplicated arrangements.

For example, if two 0.4 ml/day valves or restrictors separated by valvesare placed in parallel, the resulting flow would have a maximum of 0.8ml/day depending on the pump's capacity. On the other hand, the twovalves or restrictors, in series would yield a lower flow rate.

Various configurations of valves and restrictors may be envisioned.Configurations may be envisioned that permit multiple therapeuticsolution inlet points delivered to a single outlet, a single inlet tomultiple outlets, and various combinations. Further configurations maybe envisioned that permit a variety of dose options.

FIG. 5 depicts an exemplary method for use by the dose control module.The method 130 begins with the establishment of a prescription or a setof prescriptions as seen in block 132. A surgeon may establish theprescriptions before or during the surgery using a computer.Alternately, the prescriptions may be established using an RF signaldevice after implanting. Access to the prescriptions may be varied bytime of day, reservoir levels, bolus limitations, time-out periods, andaverage dose limits, among others.

Once implanted, the dose control module may permit the patient to selecta prescription as seen in block 134. The selection of a prescriptionmay, for example, be to initiate a bolus injection or select from apreset set of dosage rates. The patient may activate an external controlunit and transmit the desired prescription parameters to the dosecontrol module. The prescription parameters may include dose type, doserate, drug type, limits, and duration, among other data.

The dose control module then determines whether the selectedprescription is permissible as seen in block 136. Permissibility of aprescription may be a function of dosage limits, reservoir availability,and other limits and conditions included as part of the prescription setby a doctor. If the selected prescription provides dosage rates abovethe prescribed limit, the system ignores the selection as seen in block139. Alternately, if the selection is permissible, the dose controlmodule may implement the prescription as seen in block 138. To implementthe prescription, the dose control module configures the valves inaccordance with the prescription settings and other parameters.

FIG. 6 depicts another exemplary method 140. The dose control modulereceives a request for a new dosage as seen in block 141. The requestmay be received from a patient control unit or may be preprogrammed inthe dose control module. The dose control module may test the request todetermine whether it complies with dosage rules as seen in block 142.These dosage rules may include limits on average dose, periods betweenbolus treatment, and time of day restrictions, among others. If therequest does not comply, the control unit may apply a default dosage asseen in block 148.

However, if the request does comply, the system may determine how toimplement the dose. This determination may include determining thestrength of the treatment solution in the reservoir as seen in block143. The strength of solution may be affected by degradation, initialconcentration, time in place, and other factors. For example, the dosecontrol unit may determine the effective concentration of a treatmentsolution using a degradation model and then implement a flow rate thatprovides the requested dose as seen in block 144. However, thedetermination may be made before the compliance test or at other stepsin the method.

Once the dose is implemented, the dose control module monitors thelength of time the dose has been implemented. This may include storing astart time and comparing a clock value to the start time. Alternately, atimer may be started as seen in block 145.

Periodically, the system may confirm the request with an externalpatient control unit as seen in block 146. If the patient control unitconfirms the request, the timer may be restarted or a new initial timerecorded.

However, if the patient control unit does not respond or the unit doesnot confirm the dose, the dose control module may determine whether timehas expired on the does as seen in block 147. If time has not expired,the dose control module may again seek to confirm the dose. If the timeexpires, the module may return to a default dose as seen in block 148.

FIG. 7 is another exemplary method 156 for use by the system. Data isreceived as seen in block 157. The clock is then accessed in block 158.The clock may provide a time and date for comparison with stored timesor may provide a period since refilling. These times are then applied ina degradation model as seen in block 159. However, various parametersmay be used in a degradation model including model constants, storedvalues, and reservoir condition data, among others. From the degradationmodel, the system may determine a strength of the treatment solution andimplement a dosage as seen in block 160. For example, application of thedegradation model may provide an effective strength of the treatmentsolution. A flow rate may be implemented that complies with the dose.

FIG. 8 depicts a further method 150 for use by the system. A patientcontrol unit receives data from a dosage control module as seen in block151. The data may include flow rate or dosage data, parameters, andprescription options, among others. The data is stored in the patientcontrol unit as seen in block 152. Operations may then be performed onthe data. With flow rate data, the patient control unit may determine alevel in a treatment solution reservoir as seen in a block 153. If thelevel is below a threshold as determined in block 154, the patientcontrol unit may alert a patient or medical professional as seen inblock 155. However, various operations may be envisaged and the resultof these operations may be transmitted and/or stored in the dosagecontrol module.

FIGS. 9A, 9B, 9C and 9D depict an exemplary embodiment of a valve foruse by the system. The valve is enclosed in a hermetically sealedexterior housing 180. An interior housing 170 surrounds an interiorenclosure or chamber 167. The valve has an inlet port 163 and an outletport 165. The inlet port 163 and outlet port 165 connect to the interiorchamber 167. Inside the interior chamber 167 is a core, armature, orplunger 169, which may include magnetic material. The core 169 mayinclude channels 162 that permit fluid to pass by the core 169 when thecore is in the open position. The core 169 also includes heads 171 and166. FIGS. 9A and 9B depict the valve in a closed position. In theclosed position, head 166 rests on seat 168, effectively blocking theoutlet 165.

Outside of the interior chamber 167 and interior housing 170 residemagnets 178 and 172 and coils 174 and 176. When an electromagneticsignal is directed through connectors 182 and 184 and wires (not shown)to the coils 174 or 176, one of the coils 174 or 176 induces a magneticfield causing movement of the core 169. For example, if the core 169 isin the closed position as shown in FIGS. 9A and 9B, the coil 176 may beactivated, inducing a magnetic field which draws the core 169 away frommagnet 172 and into the open position. The core 169 may be held in theopen position by magnet 178 once the coil 176 is deactivated

The hermetically sealed exterior housing 180 and the interior housing170 may be made of non-magnetic material. The exterior housing 180 andinterior housing 170 may be formed of mu-metal, non-magnetic titanium,ceramic, polymer, and other compounds. Mu-metal provides protectionagainst external electromagnetic fields such as those produced by MRIs.The system may also counteract the electromagnetic fields by producingan opposing field using the coils 174 and 176.

FIGS. 9C and 9D depict the valve in the open position. To move from theclosed position to the open position, coil 176 may be activated creatinga greater magnetic attraction near the inlet 163. The core 169 thenmoves towards the inlet 163. The coil 176 may then be deactivated andthe magnet 178 holds the core in place. Fluid then travels throughchannels 162 and 164 into the chamber 169 and through the outlet 165. Toclose the valve, the coil 174 may be activated, creating a greatermagnetic field closer to the outlet, drawing the core 169 back to theclosed position. Magnet 172 holds the core in position. In this manner,the position of the core may be cycled to produce the desired dosagerate with minimum energy usage.

The permanent magnets 172 and 178 hold the core 169 in position. Thesepermanent magnets 172 and 178 also provide a redundancy protection inthe case of mechanical shock to the system. In the event of shock orchange in gravitational forces, the magnets 172 and 178 hold the core inthe set position. The magnets 172 and 178 also resist fluid pressuresfrom altering the position of the valve core 169.

The seat size of the valve may also be important for reducing unwantedmovement of the core. If the seat size is small enough, the pumppressure experienced by the core when proximate to the inlet port willexert a force less than that exerted by the magnet holding the core inplace.

However, various configurations of seats may be envisioned. Seats may bepositioned about both inlets such that fluid only flows while the coreis in a transient position. In another example, the inlet and outlet maybe reversed.

For the configuration shown, the pump pressure will influence the valveto stay in a closed position in the event that power is unavailable oreither of the magnets is damaged. Alternately, if a fail open valve ispreferred, a valve seat may be placed on the inlet and the dose channelsplaced about the outlet. The pump pressure would then influence the coreto remain in the open position if power is unavailable.

An alternate embodiment may be seen in FIGS. 10A, 10B, 10C and 10D. Inthe embodiment shown in FIG. 10A, the magnet 203 is positioned about aport 192. Coils 208 and 210 may be alternately activated to move thecore 198 into the open position near port 192 or into the closedposition near port 194. In the closed position, a head 200 may rest onthe valve seat 206, effectively closing off flow.

The core 198 may take various forms. The core 198 may be made frommagnetic material. This material may include paramagnetic material. Inwhich case, the coils and magnets would pull the core 198 into position.Alternately, the core 198 could be composed of diamagnetic material. Inwhich case, the core 198 would be pushed into position by the magnetsand coils. The core 198 may also be made from composite materials thatinclude magnetic material such as Teflon-coated ferromagnetic materials,among others. Alternately, the core 198 may be made of a non-magneticmaterial with magnetic rods or a secondary core inside.

The head may take various forms. These forms may include silicone andother biocompatible materials suitable for fitting snug against a valveseat.

As seen in FIG. 10B, the core 198 may have channels 202 and a head 200.In the closed position the head 200 may rest against a valve seat.However, in the open position, the channels 202 may permit fluid to flowaround the core 198 and through the outlet. FIG. 10C shows an alternateembodiment in which the channels 216 may be drilled through the core214. In this case, the core 214 has a head 212 that rests on the valveseat in the closed position.

However, various seats and core styles may be envisaged. For example,FIG. 10D shows a triangular core 222 that may be positioned in acylindrical chamber. The triangular core may have a head 220 that restson a valve seat effectively closing the valve. However, when open, fluidmay pass around the edges of the triangle with little restriction.Alternate embodiments may include a spherical core in an enclosure witha square cross-section. In this example, the sphere may be a siliconecoated ferromagnetic sphere. However, many embodiments may beenvisioned.

FIG. 11 depicts a further embodiment of the valve 230 as a core 238 in achamber 236. The valve has a bellows 252. Coils 248 and 250 may becycled on and off to move the core 238 through the chamber 236. When thecore 238 rests on valve seat 246, the bellows 252 may fill with thepharmaceutical solution. Alternately, when the core 238 and the corehead 242 rest against valve seat 244, the bellows 252 may drain throughthe outlet 232. One advantage to this system is that the maximum dose apatient can receive in the event of valve failure is equal to the volumeof the bellows 252.

In a similar embodiment, one end of the chamber may have channelsinstead of a valve seat. The core 238 may be positioned at that end andpermit fluid flow. In this case, the bellows will act to controlpressure fluctuations or spread out the drug delivery.

Dosage control systems including the valves of FIGS. 9, 10, and 11 haveanother advantage in that the valve position may be determined throughthe response of the coils to signals. If the core is positioned near thecoil, the signal will represent a different inductance than if the coreis further from the coil. In this manner, the system may determine valveposition and in the event of error, attempt to reposition the valve,stop flow from the pump, or alert the patient, among others.

FIG. 12 depicts an exemplary method for operating the valve. The method270 involves energizing the coil 272 to move the valve position into thedesired position. The dose control module may then test to determinewhether the core is in the correct position by sending a signal throughone or the other coils as seen in block 174. The returning signal willvary in accordance with the inductance caused by the presence of thecore. The dose control module may then analyze the signal as seen inblock 276 to determine the position of the core. Alternately, the systemmay test and analyze the signal prior to energizing the coils. Further,the system may periodically test the position of the core to ensure thatthe valve is in the appropriate position and is functioning properly.

The coils may also be used to counteract external magnetic fields suchas those produced by an MRI. The MRI may induce a current in the coils.This signal may be interpreted by a dose control module to ascertain thedirection and strength of the magnetic field. A signal may then be sentto the coils to counteract or oppose the external magnetic field. Inthis manner, valve position may be ensured and damage to the magnets orthe core prevented.

Another valve for use by the system may be seen in FIG. 13. FIG. 13represents a solenoid valve with dual armatures, wherein each armaturemay be opened by one or more coils. Valve 290 has two ports 292 and 294.These ports connect to a housing forming an interior chamber. Each porthas an associated valve seat, 302 and 314. Against these valve seats maybe valve heads and armatures 304 and 312, respectively. Each of thesearmatures is held in place by an associated spring 306 and 310,respectively. These springs, 306 and 310, may press against a springstop 308. Alternately, they may press against separate spring stops. Aspool 298 surrounds the enclosure. Coils 300 are wrapped around thespool 298. Activation of the coils 300 induces a magnetic field thatdraws the valve heads 304 and 312 away from their respective seats 302and 314 and towards spring stop 308. The armatures 304 and 312 may havea common axis of movement but move in opposite directions, toward thecenter of valve 290.

Fluid flow occurs from one port, i.e. inlet port 292, through theinterior chamber 316 and connecting chamber 320, and exists throughchamber 318 and outlet port 294.

The armatures 304 and 312 may be made of magnetic material. Heads on thearmatures may be made of silicone or a material capable of sealingagainst the valve seats. The armatures may also have channels, grooves,or holes to permit fluid flow when the head is away from the valve seat.The springs may be made of magnetic or non-magnetic material.

The hermetically sealed exterior housing 296 may be made of non-magneticmaterial. The exterior housing 296 may be formed of non-magnetictitanium, ceramic, polymer, and other compounds.

The valve system of FIG. 13 provides several redundancies. Having twosprings and valve assemblies ensures that if one valve assembly sticksopen, fluid will still be prevented from flowing by the secondoperational valve assembly. If the valve experiences a directionalmagnetic field, one valve assembly might open, however, the other wouldremain closed. Further, if a leak across a seat causes pressure to buildin the interior of the valve, the pressure will force the valveassemblies against their seats, preventing unwanted leakage.

The design of the inlet size is also important. Smaller inlet diametersprevent leaks from the inlet port by reducing the total force againstthe head. This smaller force may also permit smaller spring constants tobe used, reducing the opening force requirements and thus the powerrequirements of the coil.

An alternate embodiment may be seen in FIG. 14 in which a common spring344 presses the valve heads 342 and 346 against their respective seats.During the closed position, the coils 340 wrapped around spool 338 maybe activated to draw the valve heads 342 and 346 inward along the axisof flow, compressing spring 344. The single spring assembly removes thedouble spring redundancy and hence, the valve may be advantaged by fewparts for wear and tear.

FIG. 15 depicts a further exemplary embodiment of the valve as seen inFIGS. 13 and 14. Armatures 362 and 366 are pressed against valve seatassociated with ports 352 and 354 with at least one spring 364. A coil360 may induce a magnetic force in the armatures 362 and 366 thatopposes the spring 364. A core 368 is located between the armaturesallowing for enough space to permit movement of the armatures sufficientfor permitting fluid flow, In addition, a cover 369 is located about thecoil. The cover 369 and the core 368 are made from materials that act toguide the magnetic field and in turn strengthen the effect of thecoil-induced magnetic field on the armatures 362 and 366.

These valves, shown in FIGS. 13, 14, and 15, have the advantage of beingredundantly in a closed position. The valves also have the advantage ofalternately being in a closed position given a strong magnetic field inone direction along the axis of the valve. Such a strong magnetic fieldmay be experienced during testing, such as an MRI.

Moving the valves into an open position may require more energy thankeeping the valves open. This is a product of the inductance-producedelectromagnetic field. To open the valves, a larger amount of energymust be applied to the coil to produce. a magnetic field strong enoughto open the valves. However, once the valves are open, the magneticfield may be maintained using less energy. As such, energy may beconserved by reducing the current applied to the coils or providing atimed signal to the coils, among others.

FIG. 16 depicts an exemplary embodiment of a timed signal. The inducedmagnetic field is represented by the line 0. To produce this magneticfield, a signal A is directed to the coils. To open the valve, a longerduration pulse is provided to the coils causing the magnetic field toincrease. Once the valve is open, the pulse stops, causing the magneticfield to gradually decrease. During this gradual decrease, a currentsignal B is produced in the coil. This signal may be used forregenerating power sources or recovering energy. In this manner, powermay be conserved. Once the magnetic field reaches a minimum, the signalA may produce another pulse, increasing the magnetic field. In thismanner, the valve may be kept open using a minimal amount of energy.Alternately, a larger powered pulse may be used to open the valve and aconstant low power signal to keep the valve open.

FIG. 17 depicts an exemplary circuitry 375 for producing the signals ofFIG. 16. An induction coil 377 is associated with a valve. A powersource 376 is coupled with the coil 377 through switches 378, 379 and380, and diode 381. The switches may take various forms includingvarious transistors, four-level diodes, relays, and thyristors, amongothers. The circuitry may also include an energy collection circuitry382. A controlling circuitry may be coupled to the switches. However,various modifications to this circuitry 375 may be envisaged.

If switches 378 and 379 are closed or activated, current flows throughthe coil 377, inducing a magnetic field. Once the field is strongenough, the valve opens. In one embodiment, the magnetic forces on thearmatures in the valve overcome a spring force and open the valve. Afterinitially opening the valve, the switches 378 and 379 are used toproduce electric pulses through the coil 377 to maintain the magneticfield above a threshold value below which the valve would close orreseat.

Between pulses, the magnetic field motivates a current to flow in thesame direction as that used to induce the field. If switch 380 is closedor activated, current is directed through the diode 381 toward thepositive end of the power source. Alternately, energy may be collectedby an energy collection circuitry 382. This circuitry 382 is depicted asa capacitor. However, it may take various forms.

Various additional switches, diodes and connections may be made topermit periodic reversal of current for producing a degaussing fieldwith the coil 377. The system may also be grounded as seen in ground383. However, various modifications to the circuitry may be envisaged.

FIG. 18 is an exemplary method for use by the system. The method 370calls for energizing the coils as seen in block 372. This may beaccomplished by providing a higher amplitude pulse or a longer pulse toproduce the induced electromagnetic field. The coil may then be pulsedas seen in a block 374 to maintain the valve in an open position. Thepulsing may be used to reduce the energy requirement of the system.Further, between pulses, the induced voltage and current in the coil maybe used to recover energy.

The system may be subject to various strong external electromagneticfields, as in the case of MRI testing. The valves of FIGS. 9, 10 and 11and those of FIGS. 13, 14, and 15 may undergo these strong magneticfields when placed in a patient. It is therefore important to counteractthese strong electromagnetic fields to ensure functionality of thevalve.

FIG. 19 depicts a circuit that may be used to counteract the effects ofa strong unidirectional electromagnetic field or produce a degaussingfield. The system may test the coil 402 to determine the direction ofthe electromagnetic field. Then, an opposing electromagnetic field maybe produced in the coil by applying the correct voltage or current. Toproduce current in one direction, the switches 394 and 398 may be closedand the signal generator 392 activated. To produce current in theopposite direction, and thus an opposite electromagnetic field, switches396 and 400 may be closed while switches 394 and 398 remain open.

This circuitry may also be used to periodically change the direction ofcurrent across a coil, effectively providing a degaussing field. Thecircuitry of FIG. 17 may also be modified to recover power. Thecircuitry of FIG. 17 may be incorporated as part of signal generator392. Alternately, a modified circuitry may be placed about the coil 402.

FIG. 20 depicts an exemplary method 410. In this method, the systemtests for the electromagnetic field induced by the external, directionalelectromagnetic field. The system then applies an opposing field bysending a current in the appropriate direction through the coils as seenin a block 414.

In this manner, an external electromagnetic field may be counteracted.For the dual-head solenoid type valve, a strong unidirectional fieldwould attempt to open one side while exerting excess pressure on theother side. Neutralization of the field would ensure valve closure,reduce wear on valve parts, and prevent magnetizing the armatures. Forthe movable core valve, a strong unidirectional magnet field may placethe core in an undesired position, damage the permanent magnets andmagnetize the core, Here too, the coils may be used to neutralize thefield, Simultaneously, some of an induced current in the coils could beused to regenerate power.

Both valve types may also benefit from a reverse current periodicallyapplied to the coils. The reverse current would cause a degaussing ofmagnetism and prevent residual buildup of magnetism in either the coreor the armatures. Such a reverse current may be produced by the circuitof FIG. 19.

As such, a dose control module and valves are described. In view of theabove detailed description of the present invention and associateddrawings, other modifications and variations will now become apparent tothose skilled in the art. It should also be apparent that such othermodifications and variations may be effected without departing from thespirit and scope of the present invention as set forth in the claimswhich follow.

1. A method for controlling the flow of a fluid from an implantable drugpump device, the method comprising: storing a therapeutic solution in areservoir of the implantable drug pump device; operating a valvecomponent of the implantable drug pump device to control fluid flow fromthe reservoir and out from the implantable drug pump, wherein valvecomponent comprises (i) two or more opposing armatures within aninterior chamber of the valve component of the implantable drug pumpdevice; (ii) one or more springs placed between the armatures, whereinthe springs force the armatures against an armature's associated valveseat, wherein during operation the drug pump device induces a magneticfield with at least one coil, the magnetic field motivating thearmatures to move along a common axis in opposite directions against theforce of the one or more springs providing a path for fluid flow; andreversing, periodically, the direction of current flow through the atleast one coil to form a degaussing field.
 2. The method of claim 1,further comprising: measuring a response from the at least one coil todetermine the presence of an externally applied magnetic field.
 3. Themethod of claim 2, further comprising: inducing with the at least onecoil a magnetic field opposing the externally applied magnetic field. 4.The method of claim 1 wherein (i) the valve component is coupled to abellows, that is separate from the reservoir, and (ii) the bellows issuccessively filled and emptied of fluid during cycles of the valvecomponent during operation of the implantable drug pump device.
 5. Themethod of claim 1 wherein the valve component is adapted to preventfluid flow in the presence of an external magnetic field, having a fieldmagnitude greater than a magnitude of a field applied by the implantabledrug pump device via the at least one coil, irrespective of a fielddirection of the external magnetic field relative to the valvecomponent.